I. Background of the Invention:
This invention relates generally to an improved device for creating smooth joints between sheets of gypsum-type wallboard, and more particularly to an improved gypsum board sanding tool incorporating a dust collecting feature.
II. Discussion of the Prior Art:
In my earlier U.S. Pat. No. 4,779,385, there is disclosed a pole sander of the type involved herein in which a hollow tubular pole provides the conduit through which a vacuum may be drawn creating a negative pressure through and around the base and side surfaces of a sanding head. The sanding head is fastened to the pole by means of a universal joint and a flexible, air impervious boot is made to surround the universal joint and the lower end portion of the pole. A somewhat similar configuration is discussed in the Mehrer U.S. Pat. No. 4,062,152.
My earlier construction was found to exhibit certain drawbacks. More particularly, with only a single central opening through the back of the vacuum chamber, a lack of uniformity in the amount of vacuum developed over the working face and edges of the sanding head has been observed. Moreover, being disposed in the fluid path, the universal joint is exposed to all of the dust and debris being drawn through the sanding head and the tubular pole to the vacuum cleaning attachment. The buildup of dust and debris in the universal joint was found to prematurely wear that joint because of the abrasive properties of that dust.
It has also been found that the accordian-pleated boot used to surround the U-joint and to provide a air-tight seal between the sanding head's vacuum chamber and the interior of the hollow pole tended to be overly flexible allowing the sanding head to flip and flop about too freely, making it somewhat difficult to maintain the desired surface contact between the abrasive sheet and the wall being treated.
The device of the Mehrer patent suffers from a further drawback in not adequately providing a fluid path between the perimeter of the sanding head and the vacuum chamber. As such, only the dust and debris developed over the planar surface of the sanding head is picked up and that surrounding the perimeter falls free.